The present invention relates to a lock assembly, and more particularly to an inexpensively manufactured multi-piece plug assembly.
Numerous types of conventional lock assemblies are utilized for various applications. Some door locksets include a cylinder lock which is typically located in the door operator, such as a knob, or within a guard collar of a deadlock. Such a cylinder lock includes a cylinder body which is formed with a cylindrical opening for receipt of a cylindrically shaped plug for rotation therein. The cylinder body and plug are each formed with a plurality of alignable pin chambers which receive and support sets of spring-biased tumbler pin sets. Normally, various pins overlap a juncture line between adjacent facing surfaces of the cylinder body and the plug to prevent the plug from rotating relative to the cylinder body. This juncture line is referred to as “the shear line.”
The plug is formed with a key slot which communicates with the pin chambers so that portions of the tumbler pins extend into the key slot. When an appropriate key is inserted into the slot, bits on the key adjust the position of the tumbler pins so that upper driver pins and lower pins of the pin sets within each pin chamber are moved to locate the interface between the lower pins and the driver pins at the shear line. The shear line is then clear and the plug can be rotated within the opening of the cylindrical body to permit rotation of a driving member and subsequent activation of the lock.
Disadvantageously, the plug may be relatively difficult to manufacture due to the exacting tolerances of the multitude of pin chambers and the keyway which is formed therein. Typically, the plug is cast as a cylinder with the keyway formed therein. Then, the multiple of pin chambers are machined into the plug as a secondary operation. Although effective, this manufacturing process is relatively expensive due to the secondary machine operations.
Accordingly, it is desirable to provide a cylinder lock plug which may be manufactured in an economical manner yet maintain the exacting tolerances required for effective operation.